96 
BRITISH ENTOMOSTRACA. 
Monoculus simus, Gmelin, Syst. Nat., 1 3th edit., i, 3000, No. 25, 
1788. 
— Manuel , Encyc. meth, vii, 723, No. 18. 
— Jurine, Hist. Nat. Monoc., 129, t. 12, f. 1. 
Monoculus LiEVis, Fabricius , Ent. Syst., ii, 492, 1793. 
Monoculus exspinosus, De Geer , Mem. pour servir a PHist. Ins., 
• vii, 457, t. 27, f. 9-11, 1778. 
Monoculus conchaceus, Donovan , Nat. Hist. Brit. Ins., i, 15, t. 5,f. 1. 
Ungeschwanzter-zackiger Wasserfloh, Schaeffer, Die grim. Arm- 
Polyp, 229, 1. 1, f. 9. 
Monoculus nasutus (?), Jurine, 1. c, t. 13, f. 1. 
Monoculus pulex, Sulzer , Abgekurzte Geschichte derlnsecten, 266, 
t. 30, f. 10 *. 
Daphnia congener, Koch, Deutsch. Crust, h. xxxv, t. 13. 
Daphnia exspinosa, Koch, 1. c, h. xxxv, 1. 11. 
The shell or carapace is ovate, transparent, and smaller 
than in any of the preceding species. It is striated; the 
striae being deep, and sometimes crossing, so as to pro- 
duce a reticulated appearance, especially on the anterior 
margin, which is furnished with numerous long cilia. The 
posterior extremity is rounded, slightly serrated, destitute 
of the spine which marks the preceding species, and is 
obliquely truncate anteriorly. 
The head is obtuse, much smaller than in pulex, and 
the beak less projecting. The superior antennae are 
larger than in any of the preceding species, consisting of 
a stout joint, arising from under the beak, and five short 
setae. The filaments of the large antennae are jointed 
and plumose, but not so decidedly as in the preceding. 
The sixth segment of the body has about three small pro- 
jections from the posterior portion ; and near its upper 
part one longer, like a spur, slightly curved upwards, 
which serves to hold up, or keep back the ova from falling 
down beyond a certain distance. 
Hab . — Ponds and ditches round London, &c. ; common 
throughout the summer and autumn. Belfast, May 1849, 
W. Thompson, Esq. - 
